Ethylenediaminetriacetic acid (ED3A) and its salts (such as its alkali metal salts, including ED3ANa.sub.3) have applications in the field of chelating chemistry, and may be used as a starting material in the preparation of strong chelating polymers, oil soluble chelants, surfactants and others. Conventional routes for the synthesis of ethylenediaminetriacetic acid were achieved via its N-benzyl derivative, which was subsequently hydrolyzed in alkaline solutions to ED3ANa.sub.3, thus avoiding cyclization to its 2-oxo-1,4-piperazinediacetic acid (3KP) derivative. One example of the synthesis of ethylenediamine-N,N,N'-triacetic acid is disclosed in Chemical Abstracts 78, Vol. 71, page 451, no. 18369c, 1969. There it is stated that ethylenediamine reacts with ClH.sub.2 CCO.sub.2 H in a 1:3 molar ratio in basic solution at 10.degree. C. for 24 hours to form a mixture from which ethylenediamine-N,N,N'-triacetic acid can be separated by complexing the same with Co(III). The resulting cobalt complexes can be isolated through ion exchange.
U.S. Pat. No. 5,250,728, the disclosure of which is hereby incorporated by reference, discloses a simple process for the synthesis of ED3A or its salts in high yield. Specifically, a salt of N,N'-ethylenediaminediacetic acid (ED2AH.sub.2) is condensed with stoichiometric amounts, preferably slight molar excesses of, formaldehyde, at temperature between 0.degree. and 110.degree. C., preferably 0.degree. to 65.degree. C. and pH's greater than 7.0 to form a stable 5-membered ring intermediate. The addition of a cyanide source, such as gaseous or liquid hydrogen cyanide, aqueous solutions of hydrogen cyanide or alkali metal cyanide, in stoichiometric amounts or in a slight molar excess, across this cyclic material at temperatures between 0.degree. and 100.degree. C., preferably between 0.degree. and 65.degree. C., forms ethylenediamine N,N'-diacetic acid-N'-cyanomethyl or salts thereof (mononitrile-diacid). The nitrile in aqueous solutions may be spontaneously cyclized in the presence of less than 3.0 moles base: mole ED2AH.sub.2, the base including alkali metal or alkaline earth metal hydroxides, to form 2-oxo-1,4-piperazinediacetic acid (3KP) or salts thereof, which is the desired cyclic intermediate. In the presence of excess base, salts of ED3A are formed in excellent yield and purity. This patent also discloses an alternative embodiment in which the starting material is ED2AH.sub.a X.sub.b, where X is a base cation, e.g., an alkali or alkaline earth metal, a is 1 to 2, and b is 0 to 1 in aqueous solutions. The reaction mixture also can be acidified to ensure complete formation of carboxymethyl-2-oxopiperazine (the lactam) prior to the reaction. Formaldehyde is added, essentially resulting in the hydroxymethyl derivative. Upon the addition of a cyanide source, 1-cyanomethyl-4-carboxymethyl-3-ketopiperazine (mononitrile monoacid) or a salt thereof is formed. In place of CH.sub.2 O and a cyanide source, HOCH.sub.2 CN, which is the reaction product of formaldehyde and cyanide, may also be employed in this method. Upon the addition of any suitable base or acid, this material may be hydrolyzed to 3KP. The addition of a base will open this ring structure to form the salt of ED3A.
U.S. Pat. No. 5,284,972, the disclosure of which is hereby incorporated by reference, discloses N-acyl ED3A derivatives and a process for producing the same. The production of N-acyl derivatives of ethylenediaminetriacetic acid can be accomplished according to the following general reaction scheme: ##STR1## The starting ED3A derivative can be the acid itself, or suitable salts thereof, such as alkali metal and alkaline earth metal salts, preferably sodium or potassium salts.
Saturated N-Acyl ED3A derivatives that are the product of the foregoing reaction can be represented by the following chemical formula: ##STR2## wherein n is from 1 to 40. Where unsaturation occurs, the structure may be shown as follows: ##STR3## where n is from 2 to 40. As unsaturation increases, the formulae are: ##STR4## where n is 3 to 40; ##STR5## where n is 4 to 40; and ##STR6## where n is 5 to 40, etc.
Poly N-acyl ethylenediaminetriacetic acid derivatives, such as dicarboxylic acid derivatives having the following general formula also can be produced: ##STR7## where x is 1 to 40. Specific examples include mono and di ED3A derivatives such as oxalyldi ED3A, oxalylmono ED3A, maleylmono ED3A, maleyldi ED3A, succinoylmono ED3A, succinoyldi ED3A, etc.
In view of this relatively new technology, ethylenediaminetriacetic acid (ED3A) and its salts now can be readily produced in bulk and high yield.
Enzymes, such as proteases, lipases and amylases, are commonly used to enhance the performance of fabric detergents, dish washing liquids, hard surface cleaners, drain opening fluids, etc. By using such an enzyme in a detergent, it is possible to hydrolyze the proteins or starch residues on fabrics to such a degree that they become readily soluble in water. Thus, a more effective removal of difficult protein or starch stains, including blood, mucus, and sweat, food products, etc. can be achieved. Moreover, since insoluble proteins and starches cause dirt to adhere strongly to fabrics, increasing the protein and starch solubility helps remove dirt as well. Commercial enzymes are produced mainly by living cells such as yeasts, and are proteinaceous in nature. Enzymes with enhanced activity for commercial use are often produced by genetic engineering.
The type of enzyme used depends on the detergent formulation and application conditions, especially since any given enzyme typically exhibits a maximum effectiveness at specific pH's and temperatures. Above their peak effectiveness temperature, they usually become denatured and never regain their activity. Enzymes are often denatured or deactivated by harsh surfactants such as sodium lauryl sulfate or linear alkyl benzene sulfate that are also common to detergent formulations. It is believed that this denaturing or deactivation is due to the disturbance of the three dimensional structure of the protein. Metal ions such as copper.sup.+2, iron, nickel.sup.+2, cobalt, etc. can also deactivate enzymes, possibly by interacting with and blocking the active site of the enzyme.
It is therefore an object of the present invention to provide enzyme compatible surfactants.
It is a further object of the present invention to provide detergent compositions containing an enzyme and an enzyme compatible surfactant.
It is an even further object of the present invention to enhance the detergent power of a detergent composition with an N-acyl ED3A surfactant that is compatible with the enzyme in the detergent composition.